1=pod 2 3=head1 NAME 4 5BIO_do_handshake, 6BIO_f_ssl, BIO_set_ssl, BIO_get_ssl, BIO_set_ssl_mode, 7BIO_set_ssl_renegotiate_bytes, 8BIO_get_num_renegotiates, BIO_set_ssl_renegotiate_timeout, BIO_new_ssl, 9BIO_new_ssl_connect, BIO_new_buffer_ssl_connect, BIO_ssl_copy_session_id, 10BIO_ssl_shutdown - SSL BIO 11 12=head1 SYNOPSIS 13 14=for openssl multiple includes 15 16 #include <openssl/bio.h> 17 #include <openssl/ssl.h> 18 19 const BIO_METHOD *BIO_f_ssl(void); 20 21 long BIO_set_ssl(BIO *b, SSL *ssl, long c); 22 long BIO_get_ssl(BIO *b, SSL **sslp); 23 long BIO_set_ssl_mode(BIO *b, long client); 24 long BIO_set_ssl_renegotiate_bytes(BIO *b, long num); 25 long BIO_set_ssl_renegotiate_timeout(BIO *b, long seconds); 26 long BIO_get_num_renegotiates(BIO *b); 27 28 BIO *BIO_new_ssl(SSL_CTX *ctx, int client); 29 BIO *BIO_new_ssl_connect(SSL_CTX *ctx); 30 BIO *BIO_new_buffer_ssl_connect(SSL_CTX *ctx); 31 int BIO_ssl_copy_session_id(BIO *to, BIO *from); 32 void BIO_ssl_shutdown(BIO *bio); 33 34 long BIO_do_handshake(BIO *b); 35 36=head1 DESCRIPTION 37 38BIO_f_ssl() returns the SSL BIO method. This is a filter BIO which 39is a wrapper round the OpenSSL SSL routines adding a BIO "flavour" to 40SSL I/O. 41 42I/O performed on an SSL BIO communicates using the SSL protocol with 43the SSLs read and write BIOs. If an SSL connection is not established 44then an attempt is made to establish one on the first I/O call. 45 46If a BIO is appended to an SSL BIO using BIO_push() it is automatically 47used as the SSL BIOs read and write BIOs. 48 49Calling BIO_reset() on an SSL BIO closes down any current SSL connection 50by calling SSL_shutdown(). BIO_reset() is then sent to the next BIO in 51the chain: this will typically disconnect the underlying transport. 52The SSL BIO is then reset to the initial accept or connect state. 53 54If the close flag is set when an SSL BIO is freed then the internal 55SSL structure is also freed using SSL_free(). 56 57BIO_set_ssl() sets the internal SSL pointer of SSL BIO B<b> to B<ssl> using 58the close flag B<c>. 59 60BIO_get_ssl() retrieves the SSL pointer of SSL BIO B<b>, it can then be 61manipulated using the standard SSL library functions. 62 63BIO_set_ssl_mode() sets the SSL BIO mode to B<client>. If B<client> 64is 1 client mode is set. If B<client> is 0 server mode is set. 65 66BIO_set_ssl_renegotiate_bytes() sets the renegotiate byte count of SSL BIO B<b> 67to B<num>. When set after every B<num> bytes of I/O (read and write) 68the SSL session is automatically renegotiated. B<num> must be at 69least 512 bytes. 70 71BIO_set_ssl_renegotiate_timeout() sets the renegotiate timeout of SSL BIO B<b> 72to B<seconds>. 73When the renegotiate timeout elapses the session is automatically renegotiated. 74 75BIO_get_num_renegotiates() returns the total number of session 76renegotiations due to I/O or timeout of SSL BIO B<b>. 77 78BIO_new_ssl() allocates an SSL BIO using SSL_CTX B<ctx> and using 79client mode if B<client> is non zero. 80 81BIO_new_ssl_connect() creates a new BIO chain consisting of an 82SSL BIO (using B<ctx>) followed by a connect BIO. 83 84BIO_new_buffer_ssl_connect() creates a new BIO chain consisting 85of a buffering BIO, an SSL BIO (using B<ctx>), and a connect BIO. 86 87BIO_ssl_copy_session_id() copies an SSL session id between 88BIO chains B<from> and B<to>. It does this by locating the 89SSL BIOs in each chain and calling SSL_copy_session_id() on 90the internal SSL pointer. 91 92BIO_ssl_shutdown() closes down an SSL connection on BIO 93chain B<bio>. It does this by locating the SSL BIO in the 94chain and calling SSL_shutdown() on its internal SSL 95pointer. 96 97BIO_do_handshake() attempts to complete an SSL handshake on the 98supplied BIO and establish the SSL connection. 99For non-SSL BIOs the connection is done typically at TCP level. 100If domain name resolution yields multiple IP addresses all of them are tried 101after connect() failures. 102The function returns 1 if the connection was established successfully. 103A zero or negative value is returned if the connection could not be established. 104The call BIO_should_retry() should be used for nonblocking connect BIOs 105to determine if the call should be retried. 106If a connection has already been established this call has no effect. 107 108=head1 NOTES 109 110SSL BIOs are exceptional in that if the underlying transport 111is non blocking they can still request a retry in exceptional 112circumstances. Specifically this will happen if a session 113renegotiation takes place during a BIO_read_ex() operation, one 114case where this happens is when step up occurs. 115 116The SSL flag SSL_AUTO_RETRY can be 117set to disable this behaviour. That is when this flag is set 118an SSL BIO using a blocking transport will never request a 119retry. 120 121Since unknown BIO_ctrl() operations are sent through filter 122BIOs the servers name and port can be set using BIO_set_host() 123on the BIO returned by BIO_new_ssl_connect() without having 124to locate the connect BIO first. 125 126Applications do not have to call BIO_do_handshake() but may wish 127to do so to separate the handshake process from other I/O 128processing. 129 130BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), 131BIO_set_ssl_renegotiate_bytes(), BIO_set_ssl_renegotiate_timeout(), 132BIO_get_num_renegotiates(), and BIO_do_handshake() are implemented as macros. 133 134BIO_ssl_copy_session_id() is not currently supported on QUIC SSL objects and 135fails if called on such an object. 136 137=head1 RETURN VALUES 138 139BIO_f_ssl() returns the SSL B<BIO_METHOD> structure. 140 141BIO_set_ssl(), BIO_get_ssl(), BIO_set_ssl_mode(), BIO_set_ssl_renegotiate_bytes(), 142BIO_set_ssl_renegotiate_timeout() and BIO_get_num_renegotiates() return 1 on 143success or a value which is less than or equal to 0 if an error occurred. 144 145BIO_new_ssl(), BIO_new_ssl_connect() and BIO_new_buffer_ssl_connect() return 146a valid B<BIO> structure on success or B<NULL> if an error occurred. 147 148BIO_ssl_copy_session_id() returns 1 on success or 0 on error, or if called 149on a QUIC SSL object. 150 151BIO_do_handshake() returns 1 if the connection was established successfully. 152A zero or negative value is returned if the connection could not be established. 153 154=head1 EXAMPLES 155 156This SSL/TLS client example attempts to retrieve a page from an 157SSL/TLS web server. The I/O routines are identical to those of the 158unencrypted example in L<BIO_s_connect(3)>. 159 160 BIO *sbio, *out; 161 int len; 162 char tmpbuf[1024]; 163 SSL_CTX *ctx; 164 SSL *ssl; 165 166 /* XXX Seed the PRNG if needed. */ 167 168 ctx = SSL_CTX_new(TLS_client_method()); 169 170 /* XXX Set verify paths and mode here. */ 171 172 sbio = BIO_new_ssl_connect(ctx); 173 BIO_get_ssl(sbio, &ssl); 174 if (ssl == NULL) { 175 fprintf(stderr, "Can't locate SSL pointer\n"); 176 ERR_print_errors_fp(stderr); 177 exit(1); 178 } 179 180 /* XXX We might want to do other things with ssl here */ 181 182 /* An empty host part means the loopback address */ 183 BIO_set_conn_hostname(sbio, ":https"); 184 185 out = BIO_new_fp(stdout, BIO_NOCLOSE); 186 if (BIO_do_connect(sbio) <= 0) { 187 fprintf(stderr, "Error connecting to server\n"); 188 ERR_print_errors_fp(stderr); 189 exit(1); 190 } 191 192 /* XXX Could examine ssl here to get connection info */ 193 194 BIO_puts(sbio, "GET / HTTP/1.0\n\n"); 195 for (;;) { 196 len = BIO_read(sbio, tmpbuf, 1024); 197 if (len <= 0) 198 break; 199 BIO_write(out, tmpbuf, len); 200 } 201 BIO_free_all(sbio); 202 BIO_free(out); 203 204Here is a simple server example. It makes use of a buffering 205BIO to allow lines to be read from the SSL BIO using BIO_gets. 206It creates a pseudo web page containing the actual request from 207a client and also echoes the request to standard output. 208 209 BIO *sbio, *bbio, *acpt, *out; 210 int len; 211 char tmpbuf[1024]; 212 SSL_CTX *ctx; 213 SSL *ssl; 214 215 /* XXX Seed the PRNG if needed. */ 216 217 ctx = SSL_CTX_new(TLS_server_method()); 218 if (!SSL_CTX_use_certificate_file(ctx, "server.pem", SSL_FILETYPE_PEM) 219 || !SSL_CTX_use_PrivateKey_file(ctx, "server.pem", SSL_FILETYPE_PEM) 220 || !SSL_CTX_check_private_key(ctx)) { 221 fprintf(stderr, "Error setting up SSL_CTX\n"); 222 ERR_print_errors_fp(stderr); 223 exit(1); 224 } 225 226 /* XXX Other things like set verify locations, EDH temp callbacks. */ 227 228 /* New SSL BIO setup as server */ 229 sbio = BIO_new_ssl(ctx, 0); 230 BIO_get_ssl(sbio, &ssl); 231 if (ssl == NULL) { 232 fprintf(stderr, "Can't locate SSL pointer\n"); 233 ERR_print_errors_fp(stderr); 234 exit(1); 235 } 236 237 bbio = BIO_new(BIO_f_buffer()); 238 sbio = BIO_push(bbio, sbio); 239 acpt = BIO_new_accept("4433"); 240 241 /* 242 * By doing this when a new connection is established 243 * we automatically have sbio inserted into it. The 244 * BIO chain is now 'swallowed' by the accept BIO and 245 * will be freed when the accept BIO is freed. 246 */ 247 BIO_set_accept_bios(acpt, sbio); 248 out = BIO_new_fp(stdout, BIO_NOCLOSE); 249 250 /* First call to BIO_do_accept() sets up accept BIO */ 251 if (BIO_do_accept(acpt) <= 0) { 252 fprintf(stderr, "Error setting up accept BIO\n"); 253 ERR_print_errors_fp(stderr); 254 exit(1); 255 } 256 257/* Second call to BIO_do_accept() waits for incoming connection */ 258 if (BIO_do_accept(acpt) <= 0) { 259 fprintf(stderr, "Error accepting connection\n"); 260 ERR_print_errors_fp(stderr); 261 exit(1); 262 } 263 264 /* We only want one connection so remove and free accept BIO */ 265 sbio = BIO_pop(acpt); 266 BIO_free_all(acpt); 267 268 if (BIO_do_handshake(sbio) <= 0) { 269 fprintf(stderr, "Error in SSL handshake\n"); 270 ERR_print_errors_fp(stderr); 271 exit(1); 272 } 273 274 BIO_puts(sbio, "HTTP/1.0 200 OK\r\nContent-type: text/plain\r\n\r\n"); 275 BIO_puts(sbio, "\r\nConnection Established\r\nRequest headers:\r\n"); 276 BIO_puts(sbio, "--------------------------------------------------\r\n"); 277 278 for (;;) { 279 len = BIO_gets(sbio, tmpbuf, 1024); 280 if (len <= 0) 281 break; 282 BIO_write(sbio, tmpbuf, len); 283 BIO_write(out, tmpbuf, len); 284 /* Look for blank line signifying end of headers*/ 285 if (tmpbuf[0] == '\r' || tmpbuf[0] == '\n') 286 break; 287 } 288 289 BIO_puts(sbio, "--------------------------------------------------\r\n"); 290 BIO_puts(sbio, "\r\n"); 291 BIO_flush(sbio); 292 BIO_free_all(sbio); 293 294=head1 HISTORY 295 296In OpenSSL before 1.0.0 the BIO_pop() call was handled incorrectly, 297the I/O BIO reference count was incorrectly incremented (instead of 298decremented) and dissociated with the SSL BIO even if the SSL BIO was not 299explicitly being popped (e.g. a pop higher up the chain). Applications which 300included workarounds for this bug (e.g. freeing BIOs more than once) should 301be modified to handle this fix or they may free up an already freed BIO. 302 303=head1 COPYRIGHT 304 305Copyright 2000-2023 The OpenSSL Project Authors. All Rights Reserved. 306 307Licensed under the Apache License 2.0 (the "License"). You may not use 308this file except in compliance with the License. You can obtain a copy 309in the file LICENSE in the source distribution or at 310L<https://www.openssl.org/source/license.html>. 311 312=cut 313
